PatientPlus articles are written by UK doctors and are based on research evidence, UK and European Guidelines. They are designed for health professionals to use, so you may find the language more technical than the condition leaflets.

The choroid: what is it?

The choroid is the pigmented, highly vascular layer of the globe lying between the sclera (on the outside) and the retina (on the inside). It is one of the three components of the uveal tract and is shaped a little like the body of a rounded wine glass.

The optic nerve emerges at its base and the other two components of the uveal tract sit anteriorly (the ciliary body lies around the rim and the iris stretches over the opening. It is made up of three layers, each of which can be affected by disease processes. There is the external vessel layer, the capillary layer and the internal sheet-like Bruch's membrane.

The main function of the choroid is to nourish the outer layers of the retina but it is also thought to regulate retinal heat, to assist in the control of intraocular pressure and the pigment absorbs excess light so avoiding reflection.

Hypertensive choroidopathy

Systemic hypertension affects ocular vasculature at various levels. Within the choroid, certain anatomical and histological characteristics make it particularly susceptible to the effects of severe systemic hypertension (chronic or acute). See the separate article on Non-diabetic Retinal Vascular Disease for more detail on hypertensive retinal disease.

Choroidal detachment and haemorrhage

Nature:

The choroid detaches from the underlying sclera with an associated accumulation of serum-like fluid or blood.

Patients may be asymptomatic but they may equally complain of decreased vision or of a paracentral scotoma.

Investigations:

The diagnosis is made on examination but there may be a need for ultrasound or CT/MRI investigations if additional injury is suspected.

There may be a place for fluorescein angiography where the patient presents years later with complications such as the formation of a neovascular membrane.

Treatment:

Most patients do well with conservative management.

They will be monitored for about five years to assess for the formation of a neovascular membrane ± associated delayed bleeding. Should this occur, laser treatment may be needed.

Prognosis:

Patients with uncomplicated choroidal ruptures have a good chance of full recovery.

May cause choroidal neovascularisation, which can lead to haemorrhagic or serous macular detachment. This most often occurs during the first year after the injury but has been reported up to five years after injury.

Another complication is the formation of an epiretinal membrane. This membrane can be removed surgically.

Choroidal folds

Nature - these are parallel grooves involving Bruch's membrane. When looking at them on fundoscopy, they give the impression of a sheet of cling film that is being pulled taught centrally around the disc. There are a number of causes, including orbital disease (such as retrobulbar tumours), choroidal tumours, ocular hypotony (following significant surgery) and a number of other miscellaneous causes (idiopathic, chronic papilloedema and posterior scleritis).

Presentation - many patients are asymptomatic but they may complain of metamorphopsia or impaired vision over time.

Investigations - fluorescein angiogram.

Treatment - this depends on the underlying cause but asymptomatic folds do not require treatment.

Choroideremia - this is a very rare condition that is inherited in an X-linked recessive manner and only affects males. Patients present in the first decade of life with an inability to see in dim conditions (nyctalopia) and visual field loss.[2] A number of abnormalities can be seen both on examination of the fundus and on functional testing of the retina. Vision is usually usefully retained until about the sixth decade of life, after which there is severe visual loss. No treatment is currently available.

Gyrate atrophy - this is another inherited disorder (autosomal recessive) characterised by axial myopia (short-sightedness caused by a long axis between the front and the back of the eye) and nyctalopia. There will be chorioretinal atrophy present and elevated ornithine levels in the plasma, urine, cerebrospinal fluid and aqueous humour (due to the lack of the ornithine-degrading enzyme, ketoacid aminotransferase). The extraocular features are absent or subtle.[2] Two subgroups of patients are identified based on their response to treatment with vitamin B6 (pyridoxine): those responsive to treatment have a more slowly progressing course of the disease.

Central areolar choroidal dystrophy - an autosomal dominant inherited condition presenting in the fourth to fifth decade of life with poor central vision and nyctalopia. Both eyes tend to be affected and the prognosis is poor with severe visual loss by the sixth to seventh decade of life.

Helicoidal peripapillary chorioretinal degeneration - an autosomal dominant condition presenting in childhood characterised by strips of choroidal atrophy that variably affect the individual: there may be early age visual loss or elderly mild visual impairment.

Pigmented paravenous retinochoroidal atrophy - a rare condition usually found in young men with no clear inheritance pattern, and a good prognosis due to rarity of macular involvement.

This is a heterogeneous group of conditions characterised by chorioretinal inflammation. Some of these conditions are associated with systemic infection and they all broadly have similar treatment options: immunosuppressive therapy, laser photocoagulation, topical or systemic steroid therapy, photodynamic therapy and, most recently, antivascular endothelial growth factor agents.[6]

Acute posterior multifocal placoid pigment epitheliopathy (APMPPE)

Nature - this is an uncommon, idiopathic, bilateral, self-limiting condition. Often associated with HLA-B7 and HLA-DR2.

Presentation - third to fifth decade in life, after a 'flu-like illness in about one third of the cases: progressive subacute impairment in one eye, followed by the other a few days later.

Investigations - fluorescein angiography.

Treatment - none.

Prognosis - generally very good, although in those patients who get recurrent episodes, a residual paracentral scotoma may remain.

Serpiginous choroidopathy

Nature - uncommon idiopathic bilateral progressive disease with a prolonged, fluctuating course over many years. Relapses occur after several months of remission.

Presentation - fourth to sixth decade in life. There is unilateral blurring of vision and image distortion (metamorphopsia) with the fellow eye being affected some time later (this time period varies).

Treatment - systemic steroids have been shown to be effective in at least 50% of cases. Immunosuppressive agents are also used in order to reduce the amount of systemic steroids required long-term. Some patients may also benefit from laser photocoagulation.

Nature - possibly part of a spectrum of diseases comprising - among others - PIC, MCP and MEWDS. It is uncommon, may be unilateral or bilateral and typically affects young/middle-aged women after a flu-like illness.

Presentation - acute scotoma (worse in bright light) and photopsia. There may be an associated vitritis.

Investigations - electrodiagnostic tests are invariably abnormal.

Treatment - many use immunosuppression but its benefit hasn't been fully proven yet.

Prognosis - although one third of patients may develop recurrence and have a poorer visual outcome, the majority of patients have one episode with good visual recovery.

Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. EMIS has used all reasonable care in compiling the information but make no warranty as to its accuracy. Consult a doctor or other health care professional for diagnosis and treatment of medical conditions. For details see our conditions.